<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        var age = prompt('请输入您的年龄');
        var str = '您今年'+age+'岁啦';
        alert(str);

    </script>
</head>
<body>

</body>
</html>